1. Technical Field
The invention relates generally to backlight modules, and in particular to a backlight module with uniform brightness and a high heat dissipating efficiency. The invention also relates to a method for manufacturing a backlight module.
2. Related Art
Liquid crystal display devices are commonly used as display devices for compact electronic apparatuses such as digital cameras, personal digital assistants (PDAs), navigation satellite global positioning systems (GPSs), computer monitors, flat panel televisions (TVs) and so on. Because liquid crystals in the liquid crystal display device do not emit any light themselves, it is common for a backlight module to be disposed in the liquid crystal display device. The backlight module illuminates a liquid crystal panel of the liquid crystal display device, and the panel can thereby display clear images.
Referring to FIG. 8, a conventional liquid crystal display device 10 comprises a liquid crystal panel 20 and a backlight module 40 disposed below the liquid crystal panel 20. The backlight module 40 comprises a light source, a diffusing plate 42, a light guide plate 43, a reflective plate 44, and a housing 45. The light source has a plurality of cold cathode fluorescent lamps (CCFLs) 41 in an airtight cabinet, and is for emitting light toward the light guide plate 43. The diffusing plate 42 is interposed between the liquid crystal panel 20 and the light source, and is for diffusing received light. The light guide plate 43 is interposed between the diffusing plate 42 and the light source, and is for scattering light toward the diffusing plate 42. The reflective plate 44 is disposed below the light source. The reflective plate 44 is for reflecting at least some (and preferably nearly all) of light that is emitted from bottom and side portions of the light source back into the light guide plate 43. This reflection enhances the utilization ratio of the light. The housing 45 is disposed below the reflective plate 44, and is for assembling the reflective plate 44, the light source, the light guide plate 43 and the diffusing plate 42 onto the liquid crystal panel 20. Furthermore, a prism sheet 46 is disposed on the diffusing plate 42. The prism sheet 46 is for improving the illumination of the light that transmits to the liquid crystal panel 20.
In the typical configuration of the liquid crystal display device 10 having the backlight module 40, the CCFLs 41 are arranged in a discontinuous parallel manner. Each of the CCFLs 41 is a linear light source, which emits light by means of cathode ray stimulation of fluorescent material therein. Referring to FIG. 9, the brightness of areas of the liquid crystal display device 10 relatively far away from the CCFLs 41 (shown by broken lines) is less than that of areas nearer the CCFLs 41. Thus, a dark area 47 is likely to be formed between each two adjacent CCFLs 41. Furthermore, in order to satisfy the requirement of high brightness, a large number of the CCFLs 41 is generally disposed in the airtight cabinet. Heat generated by the CCFLs 41 may not be dissipated efficiently. This can cause problems such as unstable images and a reduced useful working lifetime of the liquid crystal display device 10.
What is needed, therefore, is a backlight module that provides uniform brightness and has a high heat dissipating efficiency.
What is also needed is a method for manufacturing the above-described backlight module.